Erecting border fences in parts of Europe in response to the current massive influx of refugees may harm wildlife. The fences can kill animals by entangling them in razor wire and will jeopardize the hard-won connectivity of species populations.

The human toll of the refugee crisis deserves the highest political attention. At the same time, many of the fences could be in violation of commitments under international conservation agreements, such as the European Commission's Habitats Directive.

With the opening of political borders during the twentieth century, Europe's large fauna have rebounded. This success is a result of trans-boundary conservation projects backed by legislation and effective management.

However, refugee fences have proliferated along the borders of Slovenia, Croatia and Hungary, for example, and more are planned along the boundaries of Latvia and Estonia with Russia. These are likely to affect brown bear, wolf, lynx and red deer species.

Mitigation measures should include adapting national conservation-management schemes to ensure the survival of newly isolated animal populations; designing the structure and placement of fences to minimize their impact on wildlife; and removing the fences at the earliest opportunity.